Lithographic apparatus and device manufacturing method

ABSTRACT

An immersion lithographic projection apparatus is disclosed in which liquid is provided between a projection system of the apparatus and a substrate. The use of both liquidphobic and liquidphilic layers on various elements of the apparatus is provided to help prevent formation of bubbles in the liquid and to help reduce residue on the elements after being in contact with the liquid.

This application is a continuation of U.S. patent application Ser. No.15/918,575, filed Mar. 12, 2018, now allowed, which is a continuation ofU.S. patent application Ser. No. 14/839,633, filed Aug. 28, 2015, nowU.S. Pat. No. 9,952,515, which is a continuation of U.S. patentapplication Ser. No. 14/266,591, filed Apr. 30, 2014, now U.S. Pat. No.9,134,623, which is a continuation of U.S. patent application Ser. No.14/107,734, filed Dec. 16, 2013, now U.S. Pat. No. 9,134,622, which is acontinuation of U.S. patent application Ser. No. 13/186,991, filed Jul.20, 2011, now U.S. Pat. No. 8,634,056, which is a continuation of U.S.patent application Ser. No. 12/411,952, filed Mar. 26, 2009, now U.S.Pat. No. 8,547,519, which is a continuation of U.S. patent applicationSer. No. 10/986,178, filed Nov. 12, 2004, now U.S. Patent No. 7,528,929,which claims priority to European patent application EP 03257195.2,filed Nov. 14, 2003 and European patent application EP 04254659.8, filedAug. 3, 2004, the entire contents of each of the foregoing applicationsherein fully incorporated by reference.

FIELD

The present invention relates to a lithographic apparatus and a devicemanufacturing method.

BACKGROUND

A lithographic apparatus is a machine that applies a desired patternonto a target portion of a substrate. Lithographic apparatus can beused, for example, in the manufacture of integrated circuits (ICs). Inthat circumstance, a patterning device, such as a mask, may be used togenerate a circuit pattern corresponding to an individual layer of theIC, and this pattern can be imaged onto a target portion (e.g.comprising part of, one or several dies) on a substrate (e.g. a siliconwafer) that has a layer of radiation-sensitive material (resist). Ingeneral, a single substrate will contain a network of adjacent targetportions that are successively exposed. Known lithographic apparatusinclude so-called steppers, in which each target portion is irradiatedby exposing an entire pattern onto the target portion in one go, andso-called scanners, in which each target portion is irradiated byscanning the pattern through the projection beam in a given direction(the “scanning”-direction) while synchronously scanning the substrateparallel or anti-parallel to this direction.

It has been proposed to immerse the substrate in the lithographicprojection apparatus in a liquid having a relatively high refractiveindex, e.g. water, so as to fill a space between the final element ofthe projection system and the substrate. The point of this is to enableimaging of smaller features since the exposure radiation will have ashorter wavelength in the liquid. (The effect of the liquid may also beregarded as increasing the effective NA of the system and alsoincreasing the depth of focus.)

However, submersing the substrate or substrate and substrate table in abath of liquid (see, for example, U.S. Pat. No. 4,509,852, herebyincorporated in its entirety by reference) means that there is a largebody of liquid that must be accelerated during a scanning exposure. Thisrequires additional or more powerful motors and turbulence in the liquidmay lead to undesirable and unpredictable effects.

One of the solutions proposed is for a liquid supply system to provideliquid on only a localized area of the substrate and in between thefinal element of the projection system and the substrate (the substrategenerally has a larger surface area than the final element of theprojection system). One way which has been proposed to arrange for thisis disclosed in PCT patent application WO 99/49504, hereby incorporatedin its entirety by reference. As illustrated in FIGS. 2 and 3, liquid issupplied by at least one inlet IN onto the substrate, preferably alongthe direction of movement of the substrate relative to the finalelement, and is removed by at least one outlet OUT after having passedunder the projection system. That is, as the substrate is scannedbeneath the element in a −X direction, liquid is supplied at the +X sideof the element and taken up at the −X side. FIG. 2 shows the arrangementschematically in which liquid is supplied via inlet IN and is taken upon the other side of the element by outlet OUT which is connected to alow pressure source. In the illustration of FIG. 2 the liquid issupplied along the direction of movement of the substrate relative tothe final element, though this does not need to be the case. Variousorientations and numbers of in- and out-lets positioned around the finalelement are possible, one example is illustrated in FIG. 3 in which foursets of an inlet with an outlet on either side are provided in a regularpattern around the final element.

A problem with having various components of the lithographic projectionapparatus (e.g., the projection system, the substrate, the substratetable, etc.) in contact with immersion liquid is that once the liquidsupply system has moved to another component or the liquid is removed,liquid residue may remain behind which may lead to liquid contaminationof other components within the lithographic apparatus. Furthermore, themovement of liquid relative to surfaces of various components in thelithographic apparatus may generate bubbles within the immersion liquidwhich may be deleterious to the optical performance of the apparatus.Further, in some immersion lithography apparatus, leakage of liquidbetween the liquid supply system and the substrate, especially duringscanning movement, may occur.

SUMMARY

Accordingly, it would be advantageous, for example, to addresscontamination by, bubbles in and/or leakage of immersion liquid in animmersion lithographic apparatus

According to an aspect of the invention, there is provided alithographic apparatus, comprising:

an illuminator configured to condition a radiation beam;

a support constructed to hold a patterning device, the patterning deviceconfigured to impart the radiation beam with a pattern in itscross-section to form a patterned radiation beam;

a substrate table constructed to hold a substrate;

a projection system configured to project the patterned radiation beamonto a target portion of the substrate; and

a liquid supply system configured to at least partly fill a spacebetween the projection system and the substrate with a liquid,

wherein the liquid has a contact angle of (a) less than 60° with theprojection system, or the liquid supply system, or both, or (b) lessthan 80° with a surface of the substrate, or (c) both (a) and (b).

If an immersion liquid has a contact angle of less than 60° with asurface, during relative movement of the immersion liquid and thesurface, the formation of bubbles in the immersion liquid may be lesslikely. Thus, if the immersion liquid is based on water, the surfaceshould be hydrophilic. A way that the immersion liquid has a contactangle of less than 60° with the substrate is to include in the immersionliquid an additive configured to reduce the surface tension of theimmersion liquid. For the types of material which the substrate, finalelement and liquid supply system are made of, an additive such as asurfactant or soap is well suited. In an embodiment, it is advantageousto have the surface tension between the immersion liquid and thesubstrate, final element and/or liquid supply system greater thanbetween the immersion liquid and air. This is likely to prevent bubbleformation due to relative movement of the immersion liquid to thesurface.

An advantageous arrangement for reducing leakage is to have theimmersion liquid have a contact angle of less than 60° with a surface ofthe final element and the liquid supply system and a contact anglegreater than 90° with a surface of the substrate and/or substrate tableand/or a substrate table mounted sensor. In this arrangement, theimmersion liquid “sticks” to the final element and liquid supply systemand slides easily over the element below the liquid supply system whichis moving relative to the liquid supply system. Thus, leakage from theliquid supply system between the liquid supply system and the elementbeneath the liquid supply system may be reduced.

Examples of surfaces with which the immersion liquid has a contact angleof less than 60° include glass, a glass ceramic, a metal oxide or ametal. The surfaces may be provided by a surface treatment which isoptionally a coating or a polymer.

According to an aspect of the invention, there is provided alithographic apparatus, comprising:

an illuminator configured to condition a radiation beam;

a support constructed to hold a patterning device, the patterning deviceconfigured to impart the radiation beam with a pattern in itscross-section to form a patterned radiation beam;

a substrate table constructed to hold a substrate;

a projection system configured to project the patterned radiation beamonto a target portion of the substrate; and

a liquid supply system configured to at least partly fill a spacebetween the projection system and (a) the substrate, or (b) a sensor, or(c) a shutter member, or (d) any combination of (a)-(c), with a liquid,

wherein the liquid has a contact angle of greater than 90° with asurface of (e) the substrate, or (f) the sensor, or (g) the shuttermember, or (h) the projection system, or (i) any combination of (e)-(h),which surface is (j) alignable with an optical axis of the apparatus, or(k) a surface of the projection system, or (l) substantially all of atop surface of the substrate table, or (m) any combination of (j)-(l).

Having a contact angle greater than 90° helps to reject the immersionliquid from the surface so that it is an easy task to leave the surfacedry without any immersion liquid residue remaining on the surface. Ifthe surface is a surface of a shutter member, this is also advantageousbecause it means that the shutter member can be easily removed (i.e.with less force) from the liquid supply system as surface tensionbetween the liquid supply system and the shutter member is unlikely todevelop to hold the shutter member to the liquid supply system.

If the immersion liquid has a contact angle of greater than 90° withsurfaces of both the substrate and the projection system, this may forma system which can advantageously be used by the liquid supply system toconfine the liquid to only a localized area of the substrate. With thissystem, the immersion liquid may be held in place in the localized areaby a plurality of gas inlets to confine the immersion liquid to thelocalized area of the substrate. This may be achieved by simply having agas pressure around a periphery of the localized area to hold theimmersion liquid in place. It would be advantageous, for example, thatthe plurality of gas inlets are positioned around the optical axis ofthe apparatus and are for directing gas in a direction with at least acomponent towards the optical axis. It may be advantageous that the gasinlets do not face directly towards the optical axis of the apparatusbut rather create a flow of gas in a circular pattern around the opticalaxis. In an embodiment, gas is blown in a plane substantially parallelto a top surface of the substrate.

A way of ensuring that immersion liquid has a contact angle of greaterthan 90° with the surface is to provide a surface that compriseselevations and depressions, wherein the distance between elevationsranges from 5 to 200 μm and the height of the elevations from 5 to 100μm and wherein at least the elevations are made of a liquidphobicpolymer or a material made durably liquidphobic.

According to a further aspect of the invention, there is provided adevice manufacturing method, comprising:

providing a liquid to a space between a projection system of alithographic projection apparatus and a substrate, the liquid having acontact angle of (a) less than 60° with the projection system, or aliquid supply system used to provide the liquid, or both, or (b) lessthan 80° with a surface of the substrate, or (c) both (a) and (b); and

projecting a patterned beam of radiation through the liquid using theprojection system onto a target portion of the substrate.

According to a further aspect of the invention, there is provided adevice manufacturing method, comprising:

providing a liquid to a space between a projection system of alithographic projection apparatus and (a) a substrate, or (b) a sensor,or (c) a shutter member, or (d) any combination of (a)-(c), with aliquid, the liquid having a contact angle of greater than 90° with asurface of (e) the substrate, or (f) the sensor, or (g) the shuttermember, or (h) the projection system, or (i) any combination of (e)-(h),which surface is (j) alignable with an optical axis of the lithographicprojection apparatus, or (k) a surface of the projection system, or (l)substantially all of a top surface of a substrate table holding thesubstrate, or (m) any combination of (j)-(l); and

projecting a patterned beam of radiation using the projection systemthrough the liquid onto a target portion of the substrate.

According to a further aspect of the invention, there is provided adevice manufacturing method, comprising projecting a patterned beam ofradiation through a liquid onto a target portion of a substrate, asurface of the substrate comprising a topcoat insoluble in the liquidand having a contact angle with the liquid of less than 80°.

According to a further aspect of the invention, there is provided asubstrate for use in immersion lithography, the substrate having aresist provided on a surface thereof and a topcoat provided on thesurface of the resist, the topcoat having a contact angle to the liquidof less than 80°.

According to a further aspect of the invention, there is provided a useof a topcoat having a contact angle of less than 80° to a liquid used inimmersion lithography to prevent bubbles sticking to a resist layer or aresist stack provided on a substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described, by way of exampleonly, with reference to the accompanying schematic drawings in whichcorresponding reference symbols indicate corresponding parts, and inwhich:

FIG. 1 depicts a lithographic apparatus according to an embodiment ofthe invention;

FIG. 2 illustrates, in cross section, a liquid supply system which maybe used with one or more embodiments of the present invention;

FIG. 3 illustrates, in plan, the liquid supply system of FIG. 2;

FIG. 4 illustrates, in cross section, an alternative liquid supplysystem according to an embodiment of the present invention;

FIG. 5 illustrates, in cross section, a liquid supply system similar tothat of FIG. 4 with further modifications according to an embodiment ofthe present invention;

FIG. 6 illustrates a substrate table mounted sensor according to anembodiment of the present invention;

FIG. 7 illustrates a liquid supply system and a shutter member, in crosssection, according to an embodiment of the present invention;

FIG. 8 illustrates a further liquid supply system according to anembodiment of the present invention;

FIG. 9 illustrates schematically in projection an element of the liquidsupply system of FIG. 8; and

FIG. 10 illustrates in cross-section a topcoat applied to a substrateaccording to an embodiment of the invention.

DETAILED DESCRIPTION

FIG. 1 schematically depicts a lithographic apparatus according to aparticular embodiment of the invention. The apparatus comprises:

-   -   an illumination system (illuminator) IL for providing a        projection beam PB of radiation (e.g. UV radiation).    -   a first support structure (e.g. a mask table) MT for supporting        a patterning device (e.g. a mask) MA and connected to first        positioner PM for accurately positioning the patterning device        with respect to item PL;    -   a substrate table (e.g. a wafer table) WT for holding a        substrate (e.g. a resist-coated wafer) W and connected to second        positioner PW for accurately positioning the substrate with        respect to item PL; and    -   a projection system (e.g. a refractive projection lens) PL for        imaging a pattern imparted to the projection beam PB by the        patterning device MA onto a target portion C (e.g. comprising        one or more dies) of the substrate W.

As here depicted, the apparatus is of a transmissive type (e.g.employing a transmissive mask). Alternatively, the apparatus may be of areflective type (e.g. employing a programmable mirror array of a type asreferred to above).

The illuminator IL receives a beam of radiation from a radiation sourceSO. The source and the lithographic apparatus may be separate entities,for example when the source is an excimer laser. In such cases, thesource is not considered to form part of the lithographic apparatus andthe radiation beam is passed from the source SO to the illuminator ILwith the aid of a beam delivery system BD comprising for examplesuitable directing mirrors and/or a beam expander. In other cases thesource may be integral part of the apparatus, for example when thesource is a mercury lamp. The source SO and the illuminator IL, togetherwith the beam delivery system BD if required, may be referred to as aradiation system.

The illuminator IL may comprise adjusting means AM for adjusting theangular intensity distribution of the beam. Generally, at least theouter and/or inner radial extent (commonly referred to as σ-outer andσ-inner, respectively) of the intensity distribution in a pupil plane ofthe illuminator can be adjusted. In addition, the illuminator ILgenerally comprises various other components, such as an integrator INand a condenser CO. The illuminator provides a conditioned beam ofradiation, referred to as the projection beam PB, having a desireduniformity and intensity distribution in its cross-section.

The projection beam PB is incident on the mask MA, which is held on themask table MT. Having traversed the mask MA, the projection beam PBpasses through the lens PL, which focuses the beam onto a target portionC of the substrate W. With the aid of the second positioner PW andposition sensor IF (e.g. an interferometric device), the substrate tableWT can be moved accurately, e.g. so as to position different targetportions C in the path of the beam PB. Similarly, the first positionerPM and another position sensor (which is not explicitly depicted inFIG. 1) can be used to accurately position the mask MA with respect tothe path of the beam PB, e.g. after mechanical retrieval from a masklibrary, or during a scan. In general, movement of the object tables MTand WT will be realized with the aid of a long-stroke module (coarsepositioning) and a short-stroke module (fine positioning), which formpart of the positioners PM and PW. However, in the case of a stepper (asopposed to a scanner) the mask table MT may be connected to a shortstroke actuator only, or may be fixed. Mask MA and substrate W may bealigned using mask alignment marks M1, M2 and substrate alignment marksP1, P2.

The depicted apparatus can be used in the following preferred modes:

1. In step mode, the mask table MT and the substrate table WT are keptessentially stationary, while an entire pattern imparted to theprojection beam is projected onto a target portion C in one go (i.e. asingle static exposure). The substrate table WT is then shifted in the Xand/or Y direction so that a different target portion C can be exposed.In step mode, the maximum size of the exposure field limits the size ofthe target portion C imaged in a single static exposure.

2. In scan mode, the mask table MT and the substrate table WT arescanned synchronously while a pattern imparted to the projection beam isprojected onto a target portion C (i.e. a single dynamic exposure). Thevelocity and direction of the substrate table WT relative to the masktable MT is determined by the (de-)magnification and image reversalcharacteristics of the projection system PL. In scan mode, the maximumsize of the exposure field limits the width (in the non-scanningdirection) of the target portion in a single dynamic exposure, whereasthe length of the scanning motion determines the height (in the scanningdirection) of the target portion.

3. In another mode, the mask table MT is kept essentially stationaryholding a programmable patterning device, and the substrate table WT ismoved or scanned while a pattern imparted to the projection beam isprojected onto a target portion C. In this mode, generally a pulsedradiation source is employed and the programmable patterning device isupdated as required after each movement of the substrate table WT or inbetween successive radiation pulses during a scan. This mode ofoperation can be readily applied to maskless lithography that utilizes aprogrammable patterning device, such as a programmable mirror array of atype as referred to above.

Combinations and/or variations on the above described modes of use orentirely different modes of use may also be employed.

Another immersion lithography solution with a localized liquid supplysystem solution which has been proposed is to provide the liquid supplysystem with a liquid confinement structure which extends along at leasta part of a boundary of the space between the final element of theprojection system and the substrate table. The liquid confinementstructure is substantially stationary relative to the projection systemin the XY plane though there may be some relative movement in the Zdirection (in the direction of the optical axis). A seal is formedbetween the liquid confinement structure and the surface of thesubstrate. In an embodiment, the seal is a contactless seal such as agas seal. Such a system with a gas seal is disclosed in U.S. patentapplication Ser. No. 10/705,783, hereby incorporated in its entirety byreference.

FIG. 4 illustrates a liquid supply system which is similar to that ofFIGS. 2 and 3 in that it provides liquid to only a localized area of thesubstrate W in a space between the substrate W and a final element ofthe projection system PL. The liquid touches both the substrate andfinal element and is continuously present between the two. The liquidsupply system of FIG. 4 comprises a seal member 10 which extends aroundthe outer circumference of a final element of the projection system PL.The seal member 10 has a seal device 15, which is in an embodiment acontactless seal device, which forms a seal between the bottom of theseal member 10 and the top surface of the substrate W. Thus, liquid 5 isconfined between the substrate W, the seal member 10 and the projectionsystem PL. The seal device 15 may be a gas seal which has a gas inletand a gas outlet such as described in U.S. patent application Ser. No.10/705,783. A liquid inlet 18 provides the liquid 5 between theprojection system PL and the substrate W. A similar liquid supply systemin which there is no seal device 15 is possible in which the liquid iscontained by capillary forces between the bottom of the seal member 10which is fixed to the projection system and the substrate W. In anembodiment, the free working distance (i.e. the distance between thebottom of the final element of the projection system and the top surfaceof the substrate W) is of the order of 3 mm±0.2 or 0.1 mm but can be aslow as 1mm.

If a localized area liquid supply system as described above is used, ithas been proposed to use a shutter member which is positionable on aside of the liquid supply system opposite the projection system suchthat the immersion liquid can be confined in the liquid supply systemand between the projection system and the shutter member. This allowsthe liquid supply system to keep liquid under the projection systemduring, for example, a substrate swap. Such a system is disclosed inUnited States patent application U.S. Ser. No. 10/705,785, herebyincorporated in its entirety by reference.

Also, there is an advantage in using imaging sensors on the substratetable under the same conditions as the substrate itself will be imaged.The sensors are used to ensure that the substrate can be correctlypositioned relative to the projection beam. These sensors include atransmission image sensor (TIS) which is a sensor that is used themeasure the position at substrate level of a projected aerial image of amark pattern at the reticle (mask) level. Typically the projected imageat substrate level is a line pattern with a line width similar to theprojection beam wavelength. The TIS measures these patterns by using atransmissive pattern with a photo detector underneath. The sensor datais used to measure the position of the mask with respect to the positionof the substrate table in up to 6 degrees of freedom. The magnificationand scaling of the projected mask are also measured by using 4 points onthe mask. As the sensor must also be capable of measuring the patternpositions and influences of all illumination settings (sigma, projectionsystem numerical aperture, all masks (binary, phase shift, etc.)), asmall line width is used. Furthermore, the sensor is also used tomeasure/monitor the optical performance of the lithographic projectionapparatus. Different measurements are implemented for measuring pupilshapes, and aberrations such as coma, spherical aberration, astigmatismand field curvature. For these measurements, different illuminationsettings are used in combination with different projected images.Another such sensor may be a projection system interferometer integratedin the lithographic apparatus (ILIAS). The ILIAS is an interferometricwavefront measurement system that performs (static) measurements onprojection system aberrations (up to Zernicke 36), as needed, for systemsetup and calibration as well as for pupil measurements. The ILIAS maybe used for monitoring and recalibration of the lithographic apparatuson a regular basis depending on the apparatus needs. A further sensormay be a dose (or spot) sensor. All of these sensors are used atsubstrate level and as such are positioned on the substrate table. Inorder to avoid the need to perform complex predictions about how animmersion liquid will affect the projection beam, it is desirable toilluminate the sensor(s) under the same conditions as the substrate isto be imaged i.e. with the immersion liquid in place between theprojection system and the sensor.

To aid in keeping the immersion liquid within the liquid supply system,it can help to make any surfaces which slide under the liquid supplysystem such as the substrate W, substrate table WT, shutter member, oneor more sensors, etc., such that immersion liquid has a contact angle ofgreater than 90°, 100°, 110° or 120° with the surface. The contact angleof a liquid to a surface is measured as the angle between the surfaceand the tangent plane of the liquid lying on that surface at a locationwhere the interface of the liquid with the outside environment, forexample air, is in contact with the surface.

The surface of the substrate will generally be a topcoat or a resistcoating or the substrate material itself. In an embodiment, all of thetop surface of the substrate table which comes in contact with immersionliquid has this property. Thus, the immersion liquid flows over thosesurfaces easily.

The surfaces of the liquid supply system and, in an embodiment, thefinal element 20 of the projection system PL or any other surfaces ofthe projection system in contact with immersion liquid are such that theimmersion liquid makes a contact angle with those surfaces of less than60°, less than 50°, less than 40°, less than 30°, less than 25°, lessthan 20°, less than 15°, or less than 10°. Thus, the immersion liquid‘sticks’ to those surfaces and so loss of immersion liquid is reduced.

There are exceptions to the above general described desiderata. Forinstance, it may be advantageous to provide a surface 22 of theprojection system which is not the final element and is above the liquidsupply system, substantially parallel with the substrate W (e.g., anannulus in shape), to have a surface with which the immersion liquidmakes a contact angle of 90° or more, 100° or more, 110° or more, or120° or more. This can help in the extraction of liquid throughextraction port 19. The one or more inlets and outlets of gas sealdevice 15 may also benefit from such a property. In contrast, the innerparts of the bottom surface of the seal member 10, radially inwardly ofthe seal device 15, may benefit from having a surface roughnessincreasing treatment applied to make the immersion liquid have a smallercontact angle with that area than with other areas.

When the substrate W is moved relative to the projection system PL(indicated by arrow 50), friction between the immersion liquid 5 and thesubstrate W may cause pressure to build up in the liquid and the level 7of immersion liquid 5 to rise on one side and the level 9 to fall on theother side. This is the result of a pressure gradient introduced intothe immersion liquid 5 and may result in gas being drawn into theexposing area of the liquid under the projection system.

It is possible to reduce the likelihood of gas being drawn into theexposing area as well as reducing the likelihood of formation of bubblesin the immersion liquid 5 in general, by providing surfaces of thesubstrate W, as well as the seal member 10 and the projection system PL,such that the immersion liquid 5 has a contact angle of less than 60°,less than 50°, less than 40°, less than 30°, less than 25°, less than20°, less than 15° or less than 10° with the surfaces (liquidphilic).This ensures that the surfaces are wetted and if the immersion liquid 5is based on water, the surfaces are hydrophilic. The surfaces concernedare the top surface 40 of the substrate W which is the surface to beimaged, the outer surface 20 of the final element of the projectionsystem PL, in particular the bottom surface, and the inner surfaces ofthe seal member 10 which confine the immersion liquid 5 to the localizedarea.

The use of such surfaces (which may of course be coatings) means thatthe surface tension between the immersion liquid and the surfaces islarger than the surface tension between the immersion liquid and thesurrounding environment (e.g. air). The effect is to optimize theremoval of all gas bubbles from the surfaces.

One way of ensuring the desired contact angle is to lower the surfacetension as much as possible in the immersion liquid. If the immersionliquid is substantially water (as is in the case of 193 nm wavelengthprojection beam), the surface tension may conveniently be lowered byadding a surfactant or soap to the immersion liquid, provided this hasno adverse effects (e.g. loss of 193 nm transmission). Thus, the risk ofenclosing gas in the immersion liquid is vastly reduced. Other factors,such as degree of roughness of the surface can also be used to improvethe liquidphilic quality of a material.

An embodiment illustrated in FIG. 5 is the same as the embodimentdescribed above with respect to FIG. 4 except as described below. InFIG. 5, the seal member 10 comprises layers which have differentinteractions with the immersion liquid 5. A first layer 100 comprises amaterial with which the immersion liquid 5 has a contact angle of lessthan 60°, less than 50°, less than 40°, less than 30°, less than 25°,less than 20°, less than 15° or less than 10° as described above. Thisensures good wetting of that layer 100 by the immersion liquid 5 andreduces the likelihood of bubbles forming on that layer 100. The layer100 is on an underside of the seal member 10 facing the substrate W andis placed closer to the optical axis of the apparatus than the sealdevice 15. On the other side of the seal device 15 is a second layer 110with which the immersion liquid has a contact angle of greater than 90°,greater than 100°, greater than 110° or greater than 120°(liquid-phobic). This second layer 110 which is also on the bottomsurface of the seal member 10 facing the substrate W has the effect ofrepelling immersion liquid 5 and thereby helps in ensuring theefficiency of the seal device 15.

Embodiments illustrated in FIGS. 6 and 7 respectively are the same asthe embodiment described above in relation to FIG. 4 and describecertain aspects of that embodiment in more detail.

The embodiment of FIG. 6 relates to through the projection systemsensors 200 which are mounted on the substrate table WT and are imagedthrough the immersion liquid 5. The embodiment of FIG. 7 relates to ashutter member 300 which may be of either type (i.e. may be a separatemember or may be part of the substrate table WT) described in U.S.patent application Ser. No. 10/705,785, hereby incorporated in itsentirety by reference.

Both embodiments make use of a surface which comes into contact with theimmersion liquid 5 with which the immersion liquid has a contact angleof greater than 90°, greater than 100°, greater than 110°, or greaterthan 120°. The use of such a surface ensures that when the sensor 200 orshutter member 300 is moved away from the liquid supply system, residueof immersion liquid on the sensor 200 or shutter member 300 is unlikely.

In more detail, FIG. 6 illustrates a sensor 200, which may be any of thekinds previously described, and comprises a detector element 210, atransmissive sensor grating 222 and an absorption element 220. Theabsorption element 220 is used to enhance the sensor contrast and thusthe overall sensor performance.

The transmissive sensor grating 222 is used for convolution of theprojected aerial image of a corresponding pattern at reticle (mask)level (4 or 5 times larger than the pattern on the sensor). Theconvolution of the transmissive sensor grating 222 with the projectedaerial image of the pattern at reticle level will provide an intensityprofile depending on the position of the transmission sensor grating 222at substrate level. With the intensity data at different substrate tablepositions, the position and shape of the aerial image can be calculated.

The sensor detector element 210 transforms the radiation that istransmitted to the open area of the grating into an electrical signal.The purpose of the absorption element 220 is to absorb part of theenergy of the projection beam by providing areas of different absorptioncharacteristics so that the sensor can achieve sufficient contrast. Inan embodiment, the absorption element 220 is made of at least one metallayer such as aluminum and/or chromium (or alloys thereof) but may bemade of layers of any metals.

In FIG. 6, the final element of the projection system PL is depicted aslens 230. In this embodiment, an immersion liquid 5, such as water, ispresent between the final element 230 of the projection system and thesensor 200. The top surface of the sensor 200 is provided with a coating240 with which the immersion liquid 5 has a contact angle of more than90°, more than 100°, more than 110°, or more than 120°.

The coating 240 serves one or more purposes. It enables easy removal ofimmersion liquid and/or prevents immersion liquid residue from remainingon the sensor. This means that measurements may also be performed usingthe sensor in gas (e.g. air), without the immersion liquid. The presenceof immersion liquid residue could result in faulty measurements. Afurther effect of the coating layer 240 is to isolate the metal of theabsorption element 220 from the immersion liquid 5 to avoid possiblecorrosion of the metal of the absorption element 220, for example by agalvanic reaction between metal layers forming the absorption element220.

FIG. 7 illustrates an embodiment of a shutter member 300 (also termed acover plate, closing plate, edge seal member, gap seal member orintermediary plate). The shutter member 300 may be a surface other thana substrate surface, perhaps an upper surface of the substrate table WTwhich is substantially co-planar with the upper surface of the substrateW and is closely adjacent to the edge of the substrate W. The area ofthe shutter member 300 is large enough so that if the substrate table WTis moved such that the projection system PL and seal member 10 arepositioned over the shutter member 300, the shutter member blocks theentire aperture of the seal member 10 to prevent liquid escaping throughthe aperture. In this position, the substrate W can be removed from thesubstrate table WT using usual substrate handling equipment.

In the embodiment illustrated in FIG. 7, it is possible for thesubstrate table WT to be moved completely away from the projectionsystem PL and the seal member 10 and for the substrate W to be removedfrom the substrate table WT and a new substrate to be placed on thesubstrate table WT.

In FIG. 7, the shutter member 300 is in the form of a plate with aprimary cross sectional area larger than that of the localized area oraperture in the seal member 10. The shape of the shutter member 300 maybe any shape so long as it covers the aperture. The shutter member 300is not a substrate and is moveable relative to both the substrate tableWT and the seal member 10 and may be attached to the seal member 10 byany means such as magnets 360 illustrated in FIG. 7.

After exposure of the substrate W the substrate table WT is moved sothat the shutter member 300 is positioned under the aperture of the sealmember 10. Once positioned under the projection system PL, the shuttermember 300 is attached to the bottom of the seal member 10 to cover theaperture. The attachment method may be, for example, by a vacuum source.The substrate table WT may then be moved out of the way to a place wherethe substrate W may be exchanged. In FIG. 7, the shutter member 300 isattached to the substrate table WT by a magnet 370 when not attached tothe seal member 10 but, if made of a non-magnetic material, may beattached by a vacuum source, for example.

The surface of the shutter member 300 which comes into contact with theimmersion liquid 5 is such that the immersion liquid 5 has a contactangle of greater than 90°, greater than 100°, greater than 110° orgreater than 120° with it. Thus, as with embodiment described inrelation to FIG. 6, when the substrate table moves and the shuttermember 300 is left behind, the seal device 15 on the seal member 10 canensure that little, if any, immersion liquid 5 is left behind.Furthermore, significantly less force will be required to remove theshutter member 300 from the seal member 10 if the surface of the sealmember is as described above, i.e., it rejects the immersion liquid. Ifthe immersion liquid is water, the surface should be hydrophobic.

An embodiment illustrated in FIGS. 8 and 9 is the same as the embodimentdescribed in reference to FIG. 4 except as described below.

In this embodiment, a different type of liquid confinement system isillustrated. The final element of the projection system PL and the topsurface of the substrate W are made of a material with which theimmersion liquid 5 has a contact angle of greater than 90°, greater than100°, greater than 110°, or greater than 120°.

The immersion liquid 5 is held in place by pressurized gas on thesurface of the liquid not in contact with the substrate W or theprojection system PL. The pressurized gas is provided through inlets 400in a seal member 10 which surrounds the immersion liquid 5. A pluralityof inlets 400 are provided and they may be of any configuration which iseffective to maintain the immersion liquid 5 in place.

It will be appreciated that FIG. 8 is schematic and that in fact thedistance between the projection system PL and the substrate W is of theorder of a few microns to a few mm so that the pressure of gas on theimmersion liquid 5 required to keep the immersion liquid in place islow.

As can be seen in FIG. 8, the seal member 10 may comprise several setsof gas inlets 400 which are at different levels above the substrate W.However, this need not be the case and, as in FIG. 9, only one level ofgas inlets 400 may be provided.

Different pressures of gas can be provided through individual inlets 400to ensure that the immersion liquid 5 is in the correct position.

The seal member 10 may be attached to the projection system PL. Thepressure of gas through inlets 400 may be controlled in a feedforward orfeedback manner depending upon the measurement of the position of theimmersion liquid 5. When the substrate W moves relative to theprojection system PL forces will be generated within the immersionliquid 5 and based on measurement or prediction of this, the pressure ofgas flowing through each of the gas inlets 400 can be adjustedaccordingly, e.g., pressure on one side may be raised above the pressureon other sides.

As can be seen from FIG. 9, the gas inlets 400 are, in an embodiment, ina direction such that the gas is projected in a direction with acomponent towards the optical axis of the apparatus. The direction liesin a plane substantially parallel to the upper surface of the substrateW though is not directed exactly towards the optical axis. It isdesirable to create a gas flow which swirls around the immersion liquid5 and this is done by angling the direction of the gas inlets 400 awayfrom the optical axis. It will be appreciated that other configurationsof gas inlets may be used.

Surfaces and Immersion Liquids

When a projection beam wavelength of 193 nm is used, the immersionliquid is likely to be substantially water. On untreated glass, waterhas a contact angle of about 70°, on untreated aluminum or stainlesssteel, the contact angle is about 80°. The contact angle is the anglethrough the liquid. Embodiments described herein apply equally to othertypes of immersion liquid.

In one or more embodiments, surfaces which are liquid-phobic (contactangle greater than 90°) or hydrophobic (if the immersion liquid iswater) are used. These surfaces are generally made of polymers such asTeflon, polyethylene, polypropylene, polyacetal, fluoro-alkyl-silanes,wax or diamond like carbon.

One particularly effective surface which results in a high contact anglebetween most liquids and surfaces has been described in PCT patentapplication WO 96/04123, hereby incorporated in its entirety byreference. This surface, termed a ‘lotus surface’, is particularlysuited to any of the embodiments described above which require a largecontact angle between immersion liquid and a surface (hydrophobicsurface) and comprises a surface structure consisting of elevations anddepressions, where the distance between the elevations ranges from 5 to200 microns and the height of the elevations ranges from 5 to 100microns. At least the elevations are made of liquidphobic polymers ormaterials made durably liquidphobic and the elevations cannot be takenoff by liquid (e.g., water) or by liquid with detergents.

In one or more embodiments, liquidphilic surfaces (contact angle lessthan 60°) or hydrophilic (if the immersion liquid is water) are used.These surfaces can be provided by a metal oxide (e.g. on the surface ofa metal) or a glass (such as quartz or Zerodur). Surfaces should behighly cleaned of foreign matter if provided with such a surfacetreatment.

Thus, the type of surface needed can be provided by the material of theelement itself, with a surface treatment if necessary, and/or by acoating on a surface of the element. For example, the substrate table WTis typically made of a structural glass or glass ceramic such asZerodur. A coating of a polymer or a lotus surface treatment could beapplied to make the surface liquidphobic. Another example might be aliquid supply system made of a polymer (e.g. Teflon) which is coated orhas a surface treatment to make it liquidphilic or made of a metal (e.g.stainless steel) surface treated (e.g. highly cleaned and polished) tomake it liquidphilic.

Another way to influence (reduce) the contact angle of the immersionliquid with the surface, is to add a surfactant to the immersion liquid.Adding a surfactant has the effect to reduce the surface tension, γ, ofthe liquid so that the bubble radius, R, of a stable bubble, which isgiven by:

$R = \frac{4\gamma}{\Delta P}$

where ΔP is the pressure difference across the interface, is reduced.Furthermore, the surface spreading coefficient S is also affected by thesurface tension so that the contact angle of the liquid on a surface canbe decreased by the addition of surfactants without changing the surfaceproperties.

Surfactants might be organic or inorganic salts (whose ions disrupt theliquid molecules). The surfactants can be of any type (e.g. anionic,cationic, zwitterionic and non ionic) and added at a concentration whichis effective to produce the desired result (usually below the criticalmicelle concentration).

Evaporation of the immersion liquid from the surface of the substratemay cause an unacceptable temperature drop of the substrate. It maytherefore be advantageous to use one or more further additions to theimmersion liquid to change the vapor pressure of the liquid to reduceevaporation.

Topcoat

In an embodiment, referring to FIG. 10, a topcoat is applied to thesubstrate, on top of the resist, to prevent gas (e.g., air) bubblessticking to the surface of the resist or the resist stack. Bubbles onthe resist during exposure may result in defects due to defocus and/ordistortion of the printed image, reducing yield. According to anembodiment, the top coat is liquidphilic (i.e., hydrophilic if theimmersion liquid is water based) and has a contact angle less than 80°,e.g. in the range of from 65 to 75°. Using surfaces with contact anglesof 65° and 72°, the number of bubble defects per substrate may bereduced to less than 10, compared to about 500 with a hydrophobictopcoat or a resist with no topcoat, under the same conditions. The useof a liquidphilic topcoat is not believed to prevent formation ofbubbles but instead prevents them from attaching to the substrate wherethey may cause defects. Bubbles that are prevented from attaching to theresist can be removed from the immersion liquid to prevent imagingdefects being caused.

Topcoats are known in dry lithography and are used to protect the resistfrom gas borne contaminants and have been proposed for use in immersionlithography. However, in order to make the topcoat insoluble in theimmersion liquid (e.g., water), a fluorinated polymer is added. Afluorinated polymer makes the topcoat liquidphobic, e.g. with a contactangle of about 118°. According to this embodiment, the amount ofadditive in the topcoat, especially fluorinated polymer, is selected toprovide the desired degree of liquidphilicity.

The topcoat should also be applied using a solvent that is incompatiblewith the resist solvent, which is commonly propylene glycol monomethylether acetate (PGMEA) or ethyl lactate, sometimes with a co-solvent ofmethyl ethyl ketone (MEK), and is desirably easily soluble in the resistdeveloper, which may be a weak (0.262 normal) alkaline solution oftetra-methyl ammonium hydroxide (TMAH). The topcoat should also bestable under intense irradiation with radiation of the exposurewavelength to be used, e.g. 248, 193 or 157 nm.

In an embodiment, there is provided a lithographic apparatus,comprising: an illuminator configured to condition a radiation beam; asupport constructed to hold a patterning device, the patterning deviceconfigured to impart the radiation beam with a pattern in itscross-section to form a patterned radiation beam; a substrate tableconstructed to hold a substrate; a projection system configured toproject the patterned radiation beam onto a target portion of thesubstrate; and a liquid supply system configured to at least partly filla space between the projection system and the substrate with a liquid,wherein the liquid has a contact angle of (a) less than 60° with theprojection system, or the liquid supply system, or both, or (b) lessthan 80° with a surface of the substrate, or (c) both (a) and (b).

In an embodiment, the liquid includes an additive configured to reducesurface tension of the liquid. In an embodiment, the additive is asurfactant, or a soap, or a salt, or any combination of the foregoing.In an embodiment, surface tension between the liquid and (i) thesubstrate, or (ii) the projection system, or (iii) the liquid supplysystem, or (iv) any combination of (i)-(iii), is greater than betweenthe liquid and air. In an embodiment, the liquid has a contact angle ofless than 60° with a surface of the projection system and the liquidsupply system and a contact angle of greater than 90° with a (i) surfaceof the substrate, or (ii) the substrate table, or (iii) a substratetable mounted sensor, or (iv) any combination of (i)-(iii). In anembodiment, the surface with which the liquid has a contact angle ofless than 60° comprises a glass, a glass ceramic, a metal oxide or ametal. In an embodiment, the surface has been surface treated. In anembodiment,n the surface has a coating or a polymer. In an embodiment,the liquid has a contact angle of less than 75° with the surface of thesubstrate. In an embodiment, the liquid has a contact angle of less than70° with the surface of the substrate. In an embodiment, the liquid hasa contact angle of less than 65° with the surface of the substrate. Inan embodiment, the liquid has a contact angle of less than 60° with thesurface of the substrate. In an embodiment, an inlet and outlet of theliquid supply system, or a part of the projection system not being afinal element of the projection system, or both, have a surface withwhich the liquid has a contact angle of greater than 90°. In anembodiment, the surface with which the liquid has a contact angle ofgreater than 90° is a surface with which the liquid has a contact angleof greater than 100°, 110° or 120°. In an embodiment, the surface withwhich the liquid has a contact angle of less than 60°, is a surface withwhich the liquid has a contact angle of less than 50°, 40°, 30°, 25° or20°.

In an embodiment, there is provided a lithographic apparatus,comprising: an illuminator configured to condition a radiation beam; asupport constructed to hold a patterning device, the patterning deviceconfigured to impart the radiation beam with a pattern in itscross-section to form a patterned radiation beam; a substrate tableconstructed to hold a substrate; a projection system configured toproject the patterned radiation beam onto a target portion of thesubstrate; and a liquid supply system configured to at least partly filla space between the projection system and (a) the substrate, or (b) asensor, or (c) a shutter member, or (d) any combination of (a)-(c), witha liquid, wherein the liquid has a contact angle of greater than 90°with a surface of (e) the substrate, or (f) the sensor, or (g) theshutter member, or (h) the projection system, or (i) any combination of(e)-(h), which surface is (j) alignable with an optical axis of theapparatus, or (k) a surface of the projection system, or (l)substantially all of a top surface of the substrate table, or (m) anycombination of (j)-(l).

In an embodiment, the liquid has a contact angle of greater than 90°with surfaces of both the substrate and the projection system. In anembodiment, the liquid supply system comprises a plurality of gas inletsconfigured to confine the liquid to a localized area of the substrate.In an embodiment, the plurality of gas inlets are positioned around theoptical axis of the apparatus and are configured to direct gas in adirection with at least a component towards the optical axis. In anembodiment, the direction is in a plane substantially parallel to a topsurface of the substrate. In an embodiment, the plurality of gas inletsare not oriented directly towards the optical axis of the apparatus soas to create a flow of gas in a circular pattern around the opticalaxis. In an embodiment, the liquid has a contact angle of greater than90° with the surface of (i) the substrate, or (ii) the substrate table,or (iii) the sensor, or (iv) the shutter member, or (v) any combinationof (i)-(iv), and the liquid has a contact angle of less than 60° with asurface of the projection system, or the liquid supply system, or both.In an embodiment, the surface with which the liquid has a contact angleof greater than 90° comprises elevations and depressions, wherein thedistance between elevations ranges from 5 to 200 μm and the height ofthe elevations from 5 to 100 μm and wherein at least the elevations aremade of a liquidphobic polymer or a material made durably liquidphobic.In an embodiment, the surface with which the liquid has a contact angleof greater than 90° is a polymer. In an embodiment, an inlet and outletof the liquid supply system, a part of the projection system not being afinal element of the projection system, or both, has a surface withwhich the liquid has a contact angle of greater than 90°. In anembodiment, the surface with which the liquid has a contact angle ofgreater than 90° is a surface with which the liquid has a contact angleof greater than 100°, 110° or 120°. In an embodiment, the surface withwhich the liquid has a contact angle of less than 60°, is a surface withwhich the liquid has a contact angle of less than 50°, 40°, 30°, 25° or20°.

In an embodiment, there is provide a device manufacturing method,comprising: providing a liquid to a space between a projection system ofa lithographic projection apparatus and a substrate, the liquid having acontact angle of (a) less than 60° with the projection system, or aliquid supply system used to provide the liquid, or both, or (b) lessthan 80° with a surface of the substrate, or (c) both (a) and (b); andprojecting a patterned beam of radiation through the liquid using theprojection system onto a target portion of the substrate.

In an embodiment, the liquid has a contact angle of less than 75°, 70°,65° or 60° with the surface of the substrate.

In an embodiment, there is provided a device manufacturing method,comprising: providing a liquid to a space between a projection system ofa lithographic projection apparatus and (a) a substrate, or (b) asensor, or (c) a shutter member, or (d) any combination of (a)-(c), witha liquid, the liquid having a contact angle of greater than 90° with asurface of (e) the substrate, or (f) the sensor, or (g) the shuttermember, or (h) the projection system, or (i) any combination of (e)-(h),which surface is (j) alignable with an optical axis of the lithographicprojection apparatus, or (k) a surface of the projection system, or (l)substantially all of a top surface of a substrate table holding thesubstrate, or (m) any combination of (j)-(l); and projecting a patternedbeam of radiation using the projection system through the liquid onto atarget portion of the substrate.

In an embodiment, there is provided a device manufacturing method,comprising projecting a patterned beam of radiation through a liquidonto a target portion of a substrate, a surface of the substratecomprising a topcoat insoluble in the liquid and having a contact anglewith the liquid of less than 80°.

In an embodiment, the topcoat has a contact angle in the range of from65 to 75°. In an embodiment, the topcoat comprises a fluorinated polymerin an amount sufficient to provide the contact angle. In an embodiment,the substrate has a resist provided on a surface thereof and the topcoatis provided on the surface of the resist.

In an embodiment, there is provided a substrate for use in immersionlithography, the substrate having a resist provided on a surface thereofand a topcoat provided on the surface of the resist, the topcoat havinga contact angle to the liquid of less than 80°.

In an embodiment, the topcoat has a contact angle in the range of 65 to75°. In an embodiment, the topcoat comprises a fluorinated polymer in anamount sufficient to provide the contact angle.

In an embodiment, there is provided use of a topcoat having a contactangle of less than 80° to a liquid used in immersion lithography toprevent bubbles sticking to a resist layer or a resist stack provided ona substrate.

In an embodiment, the topcoat has a contact angle in the range of 65 to75°. In an embodiment, the topcoat comprises a fluorinated polymer in anamount sufficient to provide the contact angle.

Although specific reference may be made in this text to the use oflithographic apparatus in the manufacture of ICs, it should beunderstood that the lithographic apparatus described herein may haveother applications, such as the manufacture of integrated opticalsystems, guidance and detection patterns for magnetic domain memories,liquid-crystal displays (LCDs), thin-film magnetic heads, etc. Theskilled artisan will appreciate that, in the context of such alternativeapplications, any use of the terms “wafer” or “die” herein may beconsidered as synonymous with the more general terms “substrate” or“target portion”, respectively. The substrate referred to herein may beprocessed, before or after exposure, in for example a track (a tool thattypically applies a layer of resist to a substrate and develops theexposed resist) or a metrology or inspection tool. Where applicable, thedisclosure herein may be applied to such and other substrate processingtools. Further, the substrate may be processed more than once, forexample in order to create a multi-layer IC, so that the term substrateused herein may also refer to a substrate that already contains multipleprocessed layers.

The terms “radiation” and “beam” used herein encompass all types ofelectromagnetic radiation, including ultraviolet (UV) radiation (e.g.having a wavelength of 365, 248, 193, 157 or 126 nm).

The term “patterning device” used herein should be broadly interpretedas referring to any device that can be used to impart a projection beamwith a pattern in its cross-section such as to create a pattern in atarget portion of the substrate. It should be noted that the patternimparted to the projection beam may not exactly correspond to thedesired pattern in the target portion of the substrate. Generally, thepattern imparted to the projection beam will correspond to a particularfunctional layer in a device being created in the target portion, suchas an integrated circuit.

A patterning device may be transmissive or reflective. Examples ofpatterning devices include masks, programmable mirror arrays, andprogrammable LCD panels. Masks are well known in lithography, andinclude mask types such as binary, alternating phase-shift, andattenuated phase-shift, as well as various hybrid mask types. An exampleof a programmable mirror array employs a matrix arrangement of smallmirrors, each of which can be individually tilted so as to reflect anincoming radiation beam in different directions; in this manner, thereflected beam is patterned. In each example of a patterning device, thesupport structure may be a frame or table, for example, which may befixed or movable as required and which may ensure that the patterningdevice is at a desired position, for example with respect to theprojection system. Any use of the terms “reticle” or “mask” herein maybe considered synonymous with the more general term “patterning device”.

The term “projection system” used herein should be broadly interpretedas encompassing various types of projection system, including refractiveoptical systems, reflective optical systems, and catadioptric opticalsystems, as appropriate for example for the exposure radiation beingused, or for other factors such as the use of an immersion fluid or theuse of a vacuum. Any use of the term “lens” herein may be considered assynonymous with the more general term “projection system”.

The illumination system may also encompass various types of opticalcomponents, including refractive, reflective, and catadioptric opticalcomponents for directing, shaping, or controlling the projection beam ofradiation, and such components may also be referred to below,collectively or singularly, as a “lens”.

The lithographic apparatus may be of a type having two (dual stage) ormore substrate tables (and/or two or more mask tables). In such“multiple stage” machines the additional tables may be used in parallel,or preparatory steps may be carried out on one or more tables while oneor more other tables are being used for exposure.

One or more embodiments of the present invention may be applied to anyimmersion lithography apparatus, in particular, but not exclusively, tothose types mentioned above. A liquid supply system is any mechanismthat provides a liquid to a space between the projection system and thesubstrate and/or substrate table. It may comprise any combination of oneor more structures, one or more liquid inlets, one or more gas inlets,one or more gas outlets, and/or one or more liquid outlets, thecombination providing and confining the liquid to the space. In anembodiment, a surface of the space may be limited to a portion of thesubstrate and/or substrate table, a surface of the space may completelycover a surface of the substrate and/or substrate table, or the spacemay envelop the substrate and/or substrate table.

While specific embodiments of the invention have been described above,it will be appreciated that the invention may be practiced otherwisethan as described. The description is not intended to limit theinvention.

1. A lithographic apparatus, comprising: a substrate table constructedto hold a substrate; a projection system configured to project apatterned radiation beam onto a target portion of the substrate; and aliquid supply system configured to at least partly fill a space betweenthe projection system and the substrate with a liquid, wherein theliquid has a contact angle of (a) less than 60° with the projectionsystem, or the liquid supply system, or both, or (b) less than 80° witha surface of the substrate, or (c) both (a) and (b).
 2. The apparatusaccording to claim 1, wherein the liquid includes an additive configuredto reduce surface tension of the liquid.
 3. The apparatus according toclaim 2, wherein the additive is a surfactant, or a soap, or a salt, orany combination of the foregoing.
 4. The apparatus according to claim 1,wherein surface tension between the liquid and (i) the substrate, or(ii) the projection system, or (iii) the liquid supply system, or (iv)any combination of (i)-(iii), is greater than between the liquid andair.
 5. The apparatus according to claim 1, wherein the liquid has acontact angle of less than 60° with a surface of the projection systemand the liquid supply system and a contact angle of greater than 90°with a (i) surface of the substrate, or (ii) the substrate table, or(iii) a substrate table mounted sensor, or (iv) any combination of(i)-(iii).
 6. The apparatus according to claim 1, wherein the surfacewith which the liquid has a contact angle of less than 60° comprises aglass, a glass ceramic, a metal oxide or a metal.
 7. The apparatusaccording to claim 6, wherein the surface has been surface treated. 8.The apparatus according to claim 6, wherein the surface has a coating ora polymer.
 9. The apparatus according to claim 1, wherein an inlet andoutlet of the liquid supply system, or a part of the projection systemnot being a final element of the projection system, or both, have asurface with which the liquid has a contact angle of greater than 90°.10. The apparatus according to claim 9, wherein the surface with whichthe liquid has a contact angle of greater than 90° is a surface withwhich the liquid has a contact angle of greater than 100°, 110° or 120°.11. A lithographic apparatus, comprising: a substrate table constructedto hold a substrate; a projection system configured to project apatterned radiation beam onto a target portion of the substrate; and aliquid supply system configured to at least partly fill a space betweenthe projection system and (a) the substrate, or (b) a sensor, or (c) ashutter member, or (d) any combination of (a)-(c), with a liquid,wherein the liquid has a contact angle of greater than 90° with asurface of (e) the substrate, or (f) the sensor, or (g) the shuttermember, or (h) the projection system, or (i) any combination of (e)-(h),which surface is (j) alignable with an optical axis of the apparatus, or(k) a surface of the projection system, or (l) substantially all of atop surface of the substrate table, or (m) any combination of (j)-(l).12. The apparatus according to claim 11, wherein the liquid has acontact angle of greater than 90° with surfaces of both the substrateand the projection system.
 13. The apparatus according to claim 12,wherein the liquid supply system comprises a plurality of gas inletsconfigured to confine the liquid to a localized area of the substrateand the plurality of gas inlets are positioned around the optical axisof the apparatus and are configured to direct gas in a direction with atleast a component towards the optical axis.
 14. The apparatus accordingto claim 12, wherein the liquid supply system comprises a plurality ofgas inlets configured to confine the liquid to a localized area of thesubstrate and the plurality of gas inlets are not oriented directlytowards the optical axis of the apparatus so as to create a flow of gasin a circular pattern around the optical axis.
 15. The apparatusaccording to claim 11, wherein the liquid has a contact angle of greaterthan 90° with the surface of (i) the substrate, or (ii) the substratetable, or (iii) the sensor, or (iv) the shutter member, or (v) anycombination of (i)-(iv), and the liquid has a contact angle of less than60° with a surface of the projection system, or the liquid supplysystem, or both.
 16. The apparatus according to claim 11, wherein thesurface with which the liquid has a contact angle of greater than 90°comprises elevations and depressions, wherein the distance betweenelevations ranges from 5 to 200 μm and the height of the elevations from5 to 100 μm and wherein at least the elevations are made of aliquidphobic polymer or a material made durably liquidphobic.
 17. Theapparatus according to claim 11, wherein the surface with which theliquid has a contact angle of greater than 90° is a polymer.
 18. Theapparatus according to claim 11, wherein an inlet and outlet of theliquid supply system, a part of the projection system not being a finalelement of the projection system, or both, has a surface with which theliquid has a contact angle of greater than 90°.
 19. The apparatusaccording to claim 11, wherein the surface with which the liquid has acontact angle of greater than 90° is a surface with which the liquid hasa contact angle of greater than 100°, 110° or 120°.
 20. A devicemanufacturing method, comprising projecting a patterned beam ofradiation through a liquid onto a target portion of a substrate, asurface of the substrate comprising a topcoat insoluble in the liquidand having a contact angle with the liquid of less than 80°.